The present invention relates to a switch fabric architecture and related techniques for implementing rapid hitless switchover.
As the use of computer and telephone networks increases, so does the need for greater bandwidth. This need spurred the growth of fiber optic networks and of protocol for transmitting data over such networks. As a result, the synchronous optical network or xe2x80x9cSONETxe2x80x9d fiber optic transmission protocol was developed.
FIG. 1 illustrates a functional block diagram of a conventional SONET network with add/drop multiplexors (ADMs) as nodes. A system administrator sets up connection routes through ADMs 110-140 to transfer data between endpoints, such as port A 100 and port B 150. For example, the system administrator may program a route from origination ADM 110 through intermediate ADM 120 to the destination ADM 130, and to do so, the system administrator must program necessary route information at each ADM.
Networks, however, do not remain static, and often must be altered to accommodate varying traffic flow. In which case, ADMs are typically reconfigured through a process known as xe2x80x9cprovisioningxe2x80x9d, whereby existing connections are dropped while new ones are added. Particularly, in relatively large networks, provisioning can require an excessive amount of time because provisioning cannot be done automatically. Moreover, ADMs are typically rendered inoperable during provisioning, thereby increasing down-time for the network.
Systems and methods consistent with the principles of the present invention provide reconfiguration of a switch without taking the switch down or losing data.
Consistent with the present invention, a switching element is provided comprising a plurality of input ports, each of which receives user information and switch configuration update data. A switch matrix is provided coupled to the plurality of input ports. The switching element also includes first and second tables coupled to the switch matrix, with the second table storing current switch configuration data. A switch matrix adjustment circuit is coupled to the first table for sensing the switch configuration update data and feeding this data to the first table. The switch matrix remains configured in accordance with the current switch configuration data while the switch configuration update data is supplied to the first table. After the switch configuration update data has been supplied to the first table, the first table is selectively coupled to the switch matrix, which is then configured in accordance with the switch configuration update data.
The switch configuration update data is typically provided within a frame, along with user information data. The switch configuration update data is thus supplied in-band, and does not require a dedicated input.
Moreover, a switch consistent with the present invention typically includes a plurality of stages or arrays of switch elements, with frames propagating through each stage substantially synchronously. Accordingly, frames do not conflict with one another as they are routed through the switch.